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who invented canning or "appertisation"?
who established the microbiological basis for food spoilage?
what is blanching?
mild heat treatment given to fruits and vegetables prior to freezing, drying and canning
when is blanching a primary method?
- before freezing and drying
- before canning
why is blanching done before freezing and drying?
for enzyme inactivation
why is blanching done before canning?
- expels intercellular gases (protects can integrity, better vacuum, better heat transfer)
- softens tissue for more compact packing)
- reduces product microbial load
which oxidative enzymes does blanching protect against?
peroxidase, catalase, polyphenol oxidase, lipase, lipoxygenase, pectin esterase
what is known as the index of blanching?
- peroxidase inactivation
- because it is very heat resistant
- wide occurrence in foods
what is blanching time?
- most vegetables (1-5min) boiling water or steam
- corn-on-cob (7-10min)
what is the blanching medium?
water, steam, hot gas, microwave
why is blanching energy intensive?
- 35% of total energy in processing
- 2/3 generally lost
- energy use: steam-water-MW-air
which types of blanching have more pollution?
- water and steam
- (air and microwave have less)
how can you make blanching more efficient?
- use an ABCO blancher (made by AAFC)
- use the heat-hold-cool approach
- steam heating and recycling
- forced air cooling (fog-jet humidified)
how are most products peeled?
which products are peeled with high pressure steam/water?
which products are peeled abrasively?
potato, carrot (roots)
which products are peeled mechanically (knives)?
apples, pears, pineapple
how are products are peeled chemically?
- lye peeling
- caustic soda (NaOH) dissolve product skin
- dip or spray product (concentration, temperature, time, agitation)
- washing in acid dip
how is a can declared "full"?
by declared fill weight
when is headspace not important?
in hot-fill process
when is headspace a must for containers?
- at high temperature
- under agitation (end-over-end and axial)
what is exhausting?
- the process of removing headspace as from cans
- reduces strain on cans and jars during retorting
- provides oxygen free environment (vacuum)
what are the three methods of exhausting?
- thermal exhausting
- steam closing
- mechanical vacuum sealing
what is thermal exhausting?
- hot filled cans conveyed through a steam chamber (exhaust box)
- steam replaces air and can is sealed while hot
- on condensation, steam leaves a vacuum energy intensive
what is steam closing?
- same principle as thermal exhausting
- instead of slow exhausting, high pressure steam injected into cans prior to closing
- more efficient
- less energy intensive
what is mechanical vacuum sealing?
- clinched cans are subjected to vacuum
- removes headspace air
- high speed vacuum treatment (may not remove dissolved air from product)
how are can dimensions expressed?
give an example?
- using 2 numbers (3 digits each) either in tin, steal, aluminum
- ex: 401x411 (means 4 and 1/16" diameter from outside edge of both double seams, by 4 and 11/16" in height (outside edge of both terminal seams)
what is the purpose of thermal processing?
- to make the product safe and shelf-stable
- reduce the number of microorganisms of public health concern to a statistically small level
- create an environment around food to suppress the growth and activity of spoilage microorganisms
what does the success of thermal processing depend on?
- removing oxygen from package
- controlling pH
- giving adequate heat treatment
- controlling the storage temperature
how can recontamination be prevented once foods have been thermally processed?
package the foods in hermetically sealed containers
what are obligate aerobes?
- microorganisms requiring oxygen to grow
- ex: most molds
what are facultative anaerobes?
- microorganisms that can either make ATP using oxygen, but if no oxygen is available, they can use fermentation instead
- ex: s.aureus
what are obligate anaerobes?
- microorganisms that grow without oxygen, some can even be killed by oxygen
- ex: c. botulinum
what is a low acid food?
- pH ≥ 4.5
- ex: all meats, fish, vegetables, most soups
what is a medium acidic food?
- pH 3.7-4.5
- ex: fruit jams, fruit cocktails, grapes, tomato, peach, pimiento, pineapple, potato salad, prune juice, vegetable juice
what are thermophylic bacteria?
grow in 35-55°C
what are mesophylic bacteria?
grow in 10-40°C
what are psychrophylic bacteria?
grow in 0-35°C
what is a high acid food?
- pH < 3.7
- ex: fruit juice, apple, berries, cherries,plum, sour pickles, sauerkraut, vinegar
what is pasteurization?
- mild heat treatment
- destruction of pathogenic microorganisms
- temporary shelf-life extension
- product refrigerated to control spoilage
- temperature applied (55-100°C)
- lower the product temperature to below 4°C within 2 hrs after pasteurization
- associated also with hermetically sealed packaging
- for low acid product with refrigeration, added acids, added sugar or added salt
what is sterilization?
- also known as appertisation
- application of heat for the purpose of shelf life extension and promotion of safety
- more severe heat treatment
- long term preservation
- "misnomer" because product not sterile
- "commercially sterile"
- temperature applied of 100-150°C, reference T-121°C
- associated with strong hermetically sealed packaging and storage at below 30°C (usually at room temp)
- environment will prevent the growth of microorganisms of public health concern and spoilage type
if a can is vacuum sealed (no obligate aerobes), what does pasteurization do to a high acid food?
- control of vegetative bacteria, yeasts, molds, and enzymes
- pathogens and spore formers inactive
- shelf stable products for fruits and acidified foods
if a can is vacuum sealed (no obligate aerobes), what does pasteurization do to a low acid food?
- only pathogens controlled
- bacterial spores active
- only short term storage at refrigerated conditions
if a can is vacuum sealed (no obligate aerobes), what does steriliization do to a high acid food?
- public health concern: c. botulinum
- bot cook - 12D process is required
- spoilage concern (non-pathogenic)
- mesophylic obligate anaerobes (more resistant than facultative types)
- heat resistant thermophiles are of no concern if stored below 30°C